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This invention is directed to silicon dioxide thin films derived from certain silsesquioxane resins, in particular, hydridosilsesquioxane resins, i.e., hydrogen silsesquioxane resins, alkyl silsesquioxane resins, or aryl silsesquioxane resins, in which the infrared reflection of a surface covered by the thin film can be varied.
Silicon dioxide (SiO2) plays a crucial role in the microelectronics industry as an insulator. Typically, the oxide is generated by direct oxidation of silicon using oxygen. A variety of plasma-based methods have also been developed to allow for lower temperature processing. These methods, however, although being capable of forming highly ordered oxides, do not generally lend themselves to the tailoring of the dielectric properties of the silicon dioxide for specific applications, and at the same time, place considerable chemical restrictions on when such oxides can be incorporated into an electrical device.
Thus, the generation of silicon oxides using certain hydridosilsesquioxane (HSQ) resins has emerged as an important alternative to such thermal and plasma-based methodologies. The use of these HSQ resins, for example, allows the properties of the derived silicon oxide to be tailored for specific applications which run the gamut from computer chips to sensors.
However, despite the apparent chemical simplicity of these systems, i.e., H, Si, and O, a detailed understanding of the structure and the reactivity of such materials, particularly under conditions experienced by an operating device, has yet to be fully realized.
In this regard, while metal-insulator-metal (MIM) devices exhibiting negative differential resistance (NDR) electrical properties are generally known, for example, as shown in U.S. Pat. No. 5,312,684 (May 17, 1994), and U.S. Pat. No. 5,403,748 (Apr. 4, 1995), the chemical basis for the striking changes in resistance which occur as a function of an applied voltage or current is not fully understood.
In probing the nature of changes in the dielectrics of such devices, it was unexpectedly discovered that an MIM device could be designed to allow for its simultaneous electrical and spectroscopic characterization, and these characteristics of the device are considered unique.
The invention relates to varying the infrared reflection of a surface covered by a silicon dioxide thin film derived from a silsesquioxane resin. The resin can be, for example, a hydridosilsesquioxane resin, an alkyl silsesquioxane resin, or an aryl silsesquioxane resin. Hydridosilsesquioxane resins are representative, and used hereafter in referring to silsesquioxane resins in general. The concept involves:
(i) directing a beam of infrared radiation to a metal-insulator-metal device containing the silicon dioxide thin film derived from hydridosilsesquioxane resin,
(ii) applying an electric potential difference across the metal-insulator-metal (MIM) device containing the silicon dioxide thin film derived from hydridosilsesquioxane resin, and
(iii) monitoring variation in the infrared reflection spectrum of the MIM device in response to the electric current flowing through the silicon dioxide thin film as the frequency of incident radiation is varied.
These and other features of the invention will become apparent from a consideration of the detailed description.